Trapezoidal cavity magnetron



E. C. OKRESS EI'AL TRAPEZOIDAL CAVITY MAGNETRON Filed Oct. 15, 1942INVENTORS z ATTORNEY Sept. 5, 1950 Patented Sept. 5, 1950 2,529,9 5TRAPEZOlDAL CAVITY Ernest C. O kress and Ilia E. Mouromtseff, Montclair,N. J., assignors to Westinghouse Elec ic Corporation, East Pittsburgh,2a.; a corpgration of Pennsylvania Application October 15, 19.42, SerialNo. 462, 13.?

4. Claims. (01. 250,27 .5)

This invention relates ;to generators of high frequency electricity,-and particularly those of the type called magnetrons.

The principal objectrof our invention, generally considered, is animproved nagnetron for energy in the regionof centimeter wavelengths andamethod of manufacture.

Another object of our invention is the manufactureo'f .magnetrons by amethod which avoids the necessity of very accurate machining.

.A further object of our invention is to simplify and cheapen theconstruction of magnetrons.

A still further object of our invention is to increase the permissivetolerances in the manufacture of magnetrons.

Other objects and advantages of the invention, relating to theparticular arrangement and construction of the various parts, willbecome apparent as therdescription proceeds.

Referring to the drawings Fig. 1 is a sectional View onthe line I-I ofFig. 2, in the direction of the arrows, with parts in evelation, of amagnetron embodying our invention.

Fig. 2 is a perspective view on the line -II--II of Fig. 1, in thedirection of the arrows, with parts in elevation.

Fig. 3 is a sectional perspective View of a blank which is desirablyused in manufacturing the body member of the magnetron.

Fig. 4 is a perspective View of oneof the partition elements of amagnetron embodying our inyention.

Fig. :5 is a fragmentary view corresponding to Fig. l but showing amodification.

As pointedout in the Okress application, Serial No. 460,376, filedOctober 1, 19.42, and owned by the assignee of the present application,resonant cavity magnetrons, such as those in the 10 centimeter range,have previously been constructed as there illustrated in Fig..12, thatis, with generally cylindrical cavities disposed about ,a central pocketadapted to receive the cathode andcommunicating therewith.

In said application it is shown how accurate machining may be avoided bya modified construction in which slots took the place of the generallycylindrical cavities, three forms being theredisclosed; first, inwhich-the slots were, of generally uniform Width and separated bypartitions generally trapezoidal or sector shaped in section on a planeperpendicular to the axis; second, in which said slots were generallytrapeaoida l or sector and separated by generally trapezoidal or sectorshaped partitions; and

ma ne n H cqn ins a housing d 01' third, in which said slots aregenerally trapezoidal or sector shaped and separated by relatively thinpartitions or suchgenerally rectangular in section. it is also shownthat such ;'i I nproved constructions resulted, not only 'in avoidnsaccurate maichining but also n substantially reducing ;thewavelengthsensitivity.

In accordance with the present invention we havedevised animprovedconstruction of magnetrqns with generally trapezoidal or sectorap d a itie as w l aw mpmv methed 9 manufacture.

' Reierr-ing to the drawings in detail, and first considering theembodiment of our invention anode portion t; of oxygen-free,high-conductivity copper having relatively thin, that is,considerablythinner than the radial thickness of said .body 2, plates orvanes l fi, t, :5, 1s, :1, s, is. and 2i refe b f rm e en u s eepe alloy(described by smith in I. and

. 'I fech. Pub. N 0.3.7.0) which platesdefine generally triangular,trapezoidal or sector shaped pockets 23%, 24, 25, 26,171, .28, 29 andBlitherebetWeen, all

of saidpoclgets communicating with a central chamber or pocket 32 wherean oxide coated n cke ase cathe .33 i p tioned.

oax a t rm na o Out e d '34 i th p s embod ment ssh wn t one by havingits inner end portion curved or looped back on itself and connected tothe inner peripheral portion of the housingmember, as indicated at .55.ilnthe present instance the terminalmember .34 has i a e fi itap fill=pQ 1liQ i0m l9 tungsten and its small or inner portion formed ofelectrolytic copper, and is enclosed in a tuh lar o a nstfiiha ins a a lflan e 3! threaded as indicated at 38 for a coaxial capacitive cablecoupling, which may correspond with the threaded portion 25. of theRigrodet al. inte t, ,lio zg osml, dated Sept. 24, 1946. This ea in ...dr b thread n c ed r t cylindr c Iwrti. v l a nd e '38- .Th t mi a is deir en w t respeet th es nsi a by e n of a min #lp l or soft'borosilieateglass bead 4! between t sam an a, c li drica .q n u m mbe A wh ch m ybefo' n v of .K va (w ic s-a alloy containing 28.7 to 29.2% nickel, 17.3to 1 -53% Qba 2i9 t .14% ir no mor tha .06% carbon, not more than .5%manganese, and not more than .2% silicon) or other suitable ma- ,terial.The inner end of this conductor member is desirably connected byeutectic gQld-copper 3 solder to a steel ring 43 and the combinationsecured to the flange portion 37 by BT solder, as shown most clearly inFig. 1. 31" solder melts at about 779 C. and is 72% silver and 28%copper.

The cathode 33 in the present embodiment is shownas consisting of ahelicaltungsten filament 44 enclosed in an electron-emitting housing 45composed of a mixture of oxides of strontium, barium and calcium on anickel sleeve and supplied with power from a suitable source by tungstenleads 45 and 47.. These leads project through copper casings 48 and 49,held in place as described in connectionwith the Okress application,Serial No. 460,376, previously referred to, which also shows how thepower may be supplied to the cathode including the use of filters.

Figs. 3 and 4 show the blanks which are desir ably employed to make themagnetron body during the process of manufacture. After the design, wedesirably start with a plurality of plates 5i, desirably of uniformthickness and numerically corresponding with the pockets, in thisinstance eight. These plates are desirably formed of selenium copperalloy or other similar metal, and are relatively thin althoughsufficiently heavy to provide a rugged construction.

We then take a shell portion 52 which is generally cylindrical on itsexterior, but relatively thinned toward its ends as indicated at 53 and54,

to leave an inwardly extending annular boss 55. This boss is, in turn,slotted or grooved longitudinally or parallel to the axis, as indicatedat 56 to a width so as to snugly receive the plates 5! and leaveinwardly extending sections 57, nu

merically corresponding with the number of pockets desired in thefinished magnetron, in this instance eight. The plates 51 are thenfitted in the slots 55, as by means of a jig, and soldered in place asindicated at 58. This soldering is desirably effected with the use of BTsolder or upper and lower copper cover members 59 and BI to the body, asshown in Fig. 2, with RT solder applied at the joints. RT solder meltsat about 682 C. and is 60% silver, 25% copper, and

15% zinc. The whole assembly may be exposed in a hydrogen furnace andbrought to the melting temperature of the solder, that is not highenough to melt the interior BT soldered connec-= tions, in order toeffect such a union.

Referring now to the embodiment of our in- I vention illustrated in Fig.5, there is shown a magnetron Ii consistingof a body or anode portion 2which, like the magnetron II, is desirably formed of copper and hasselenium copper alloy partitions, like the partitions of the precedingembodiment, only those numbered 15 Hi Il and I8 being shown, projectinginwardly from the peripheral portion 22 and separated by pockets likethose of the preceding embodiment,

only those pockets numbered 25 26 2'! and 28 being shown. 'All of thesepockets communicate with a central chamber 32 where a cathode may bepositioned as in the first embodiment.

In the present embodiment, the housing or anode member !2 is formed bytaking a plain hollow cylinder and connecting radially projectingpartition wall members in place by means of BT solder, indicated at 58*,said plates being desirably held with their outeredges, as by means of ajig, in abutting engagement with the inner surface of the cylindricalouter member 22 while in a hydrogen furnace where the soldering iseffected, as in the preceding embodiment.

In the present embodiment we have shown an alternative terminal 34which, like the terminal 35 of the Okress application, Serial No.460,376, previously referred to, has large and tapering portionsdesirably formed of tungsten and a small or inner portion formed ofelectrolytic copper;

and enclosed in a tubular copper casing 36 corresponding with the casing36 of the preceding embodiment, and centered with respect thereto in asimilar manner.

In the present embodiment, however, the inner portion of the terminal 375*, instead of being bent back on itself and connected to the outercylindrical portion of the housing, extends to one of the partitionplates, such as that designated Hi passing into a recess 35 thereof, andsecured thereto in any desired manner, as by means of BT solder. It willbe noted that such. a coupling may be used in the preceding embodiment,or that of the preceding embodiment used in this embodiment,interchangeably, within the spirit and scope of our invention.

In both embodiments of our invention the portions l3, Id, etc. or l5 I6etc. projecting inwardly from the peripheral portion 22 or 22 are allgenerally thin and of uniform thickness, like the slots 23 to 29,inclusive and 3! of the first embodiment of the Okress application,Serial No. 460,37 6, previously referred to, that is, the slots orpockets therebetween aregenerally triangular, trapezoidal, or sectorshaped in section. In all the embodiments, however, the innercircumferential width of each pocket is uniform and may correspond withthe uniform circumferential width of the separating partitions,notwithstanding the variation in outer circumferential width of theseparts, although this correspondence is not essential.

Magnetrons with sector shaped pockets, like those of the presentinvention, are of lighter weight and have greater efficiency and powercapacity than those with slotted pockets, relatively narrow, asillustrated in Fig. 1 of said Okress application, Serial No. 460,376,previously referred to. This is because the impedance of the generallytriangular, trapezoidal or sector shaped slot or pocket at the slotaperture is much higher than that of the slot of uniform width, andhence such a pocket shape results in a much better match for theelectronic field impedance than in the case of a magnetron with thinslots of uniform width. The wavelength sensitivity for pockets of thepresent embodiment, with regard to their structural parameters, isbetween that of the rectangular or thin slot and the conventionalcylindrical cavity structure previously referred to.

From the foregoing, it will be seen that we have provided an improvedmagnetron and method of manufacture which avoids the necessity ofaccurate machining, simplifies and cheapens the construction, increasesthe permissive tolerances, and economizes in the use of material.

Although preferred embodiments of our invention have been disclosed, itwill he understood that modifications may be made within the spirit andscope of the appended claims.

We claim:

1. A magnetron housing formed as an outer generally cylindrical hollowconductive portion having longitudinal grooves from which flat sidedpartitions project inwardly defining a central cathode cavitycommunicating with chambers generally sector shaped in section on aplane perpendicular to the axis and disposed thereabout, a cathodeassembly disposed in said cavity, leads from said cathode assemblyprojecting through said hollow cylindrical portion to outside of saidhousing, an output lead extending into said housing in a generallyradial direction, curved backward and united to the inner surface ofsaid housing, and a conductor casing in contact with and projecting fromsaid housing and disposed coaxial with respect to said lead.

2. A magnetron housing comprising a hollow cylindrical portion ofoxygen-free high-conductivity copper from which parallel-sided walls ofselenium copper alloy project inward in generally radial directionsdefining a central cavity communicating with pockets disposedtherearound, the outer edge portions of said walls fitting in grooves insaid cylindrical portion and secured in place by solder.

3. A magnetron comprising a cathode and a hollow cylindrical conductiveportion housing said cathode, a plurality of parallel-sided Walls ofconductive material difierent from that of said cylindrical conductiveportion encircled thereby axially shorter than said cylindrical portion,and projecting from the inner surface thereoi in generally radialdirections defining a central cathode cavity communicating with pocketsdisposed therearound, the outer edge portions of said Walls fitting ingrooves in the inner surface of said hollow conductive portion and heldin place by solder, and cover members secured to the parts of saidcylindrical portion which project axially beyond said walls.

4. An electron-discharge device comprising: a cathode; and an anodestructure spaced from and surrounding said cathode and including aplurality of anode members, each pair of adjacent anode memberscomprising vanes secured in inwardly opening slots in a peripheralportion of said structure, thereby defining therewith a cavityresonator, said vanes having substantially straight side walls definingcavities expanding for an appreciable distance between the inner andouter ends thereof, leads from said cathode projeoting through saidanode structure to outside of said device, an output lead extending intosaid structure in a generally radial direction, curved backward andunited to the inner surface of the outer portion of said structure, anda conductor casing in contact with and. projecting outwardly from saidouter portion and disposed coaxial with respect to said lead.

ERNEST C. OKRESS. ILIA E. MOUROMTSEFF.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,547,836 Steenstrup July 28,1925 1,666,833 Rhodes et al. Apr. 17, 1928 2,063,342 Samuel Dec. 8, 19362,129,713 Southworth Sept. 13, 1938 2,167,201 Dallenbach July 25, 19392,247,077 Blewett et al. June 24, 1941 2,270,777 Von Baeyer Jan. 20,1942 2,295,396 George Sept. 8, 1942 2,304,186 Litton Dec. 8, 19422,408,235 Spencer Sept. 24, 1946 FOREIGN PATENTS Number Country Date509,102 Great Britain July 11, 1939 215,600 Switzerland Oct. 16, 1941527,131 France July 18, 1921

